Biological molecules Flashcards
1
Q
What is an ionic bond
A
A type of bond formed through the attraction of ions with opposing charges
2
Q
What is a covalent bond
A
A type of bond formed through the sharing of outer shell (Valence) electrons, which fills the outer shells to form a stable molecule
3
Q
What is a hydrogen bond
A
A type of bond formed through the attraction of polar molecules with opposing dipoles
4
Q
What is a monomer
A
A small, single, repeatable molecule that can bond to others to form a polymer
5
Q
What are some examples of monomers
A
Nucleotides, Monosaccharides, Amino acids
6
Q
What is a polymer
A
A large molecule made up of many similar / identical monomers bonded together
7
Q
What are some examples of polymers
A
DNA, Polypeptides, Polysaccharides
8
Q
How are polymers formed
A
Through a condensation reaction that bonds two or more monomers together
9
Q
How are monomers formed
A
Through a hydrolysis reaction that breaks down / hydrolyses the polymer back into monomers
10
Q
What is a condesation reaction
A
A reaction where the formation of the bonds in a product produces a molecule of water
11
Q
What is a hydrolysis reaction
A
A reaction where the break down / hydrolysis of the bonds in a product requires a molecule of water
12
Q
What are the three types of carbohydrate
A
Monosaccharides, Disaccharides, Polysaccharides
13
Q
Which of the three types of carbohydrates are sugars
A
Monosaccharides and Diaccharides
14
Q
Which of the three types of carbohydrates are polymers
A
Polysaccharides
15
Q
What are the two primary uses of carbohydrates
A
Energy store and structural material for membranes and walls
16
Q
What is the ratio of Hydrogen:Oxygen in a carbohydrate
A
2:1
17
Q
What is the chemical formula for glucose
A
c6h12o6
18
Q
What shaped sugar is glucose
A
Hexose
19
Q
What are alternative forms of a hexose sugar called
A
Isomers
20
Q
What are some isomers of glucose
A
Fructose, Galactose, Ribose
21
Q
What is an isomer
A
A molecule with the same chemical formula but a different structural formula / lay out
22
Q
What is a monosaccharide
A
A single sugar monomer
23
Q
What is the general formula of a monosaccharide
A
(CH2O)n
- n can be anywhere from 3 to 7
24
Q
How can you identify a monosaccharide by taste
A
If the sample tastes sweet
25
What are the two forms of glucose monosaccharide monomers
Alpha and beta
26
What is a disaccharide
A simple, dual sugar molecule formed through the condensation reaction of two monosaccharide monomers bonded together by a glycosidic bond
27
What is the general formula of all disaccharides
C11H22O11
28
How is the disaccharide maltose formed
Through a condensation reaction forming a C1 - 4 glycosidic bond between two molecules of alpha glucose
29
How is the disaccharide lactose formed
Through a condensation reaction forming a C1 - 4 glycosidic bond between one molecule of alpha glucose and one molecule of galactose
30
How is the disaccharide sucrose formed
Through a condensation reaction forming a C1 - 4 glycosidic bond between one molecule of alpha glucose and one molecule of fructose
31
What is the main function of monosaccharides and Disaccharides
To store energy
32
What is a polysaccharide
A large polymer comprised of many monosaccharides bonded together through glycosidic bonds formed in condensation reactions
33
Are monosaccharides and disaccharides soluble
Yes
34
Are polysaccharides soluble
No
35
Which polysaccharide is responsible for plant energy storage
Starch
36
Which polysaccharide is responsible for mammal energy storage
Glycogen
37
Which polysaccharide is responsible for structural materials
Cellulose
38
What are the two forms of starch
Amylose and Amylopectin
39
What is the structure of amylose
Long, unbranched, coiled chain of alpha glucose molecules bonded together by condensation reactions forming C1-4 glycosidic bonds, with a reducing end to stimulate hydrolysis
40
What is the structure of amylopectin
Long, highly branched, uncoiled structure of alpha glucose molecules bonded together by a mix of C1-4 and C1-6 glycosidic bonds
41
How is starch overall adapted to its functions
- Compact - beneficial for storing high volumes in a small space
- Insoluble - beneficial for not affecting water potential
- Large - Beneficial for containment
- Large surface area and high amount of exposed reducing ends - Beneficial for quick hydrolytic energy production
42
What is the structure of glycogen
Very highly branched coiled polymer comprised of many alpha glucose monomers bonded together by a combination of C1-4 and C1-6 glycosidic bonds formed in condensation reactions
43
How is glycogen different to amylopectin structurally
- Higher degree of branching
- Shorter branches (8-12 on average)
44
How is glycogen adapted for its function
- Compact - beneficial for storing high volumes in a small space
- Insoluble - beneficial for not affecting water potential
- Large - Beneficial for containment
- Large surface area and high amount of exposed reducing ends - Beneficial for quick hydrolytic energy production
45
What is the structure of cellulose
Straight chains of alternating beta glucose at 180 degrees bonded together by C1-4 glycosidic bonds formed through condensation reactions
46
Why does cellulose have alternating beta glucose molecules
Very high bond tension
47
How do chains of cellulose bond together to form parallel layers
Cross linking via hydrogen bonding
48
What is the progression of structure for cellulose polysaccharides
Cellulose chains -> microfibrils -> macrofibrils
49
How is cellulose adapted to its functions
- Cross linking - prevents the breakdown of the polymer for energy
- High volumes of hydrogen bonding - Increases structural rigidity and strength
50
What type of molecule are lipids
Macromolecules
51
Why are large lipid molecules not classes as polymers
They are not made up of
a repeating monomer
52
Are lipids soluble
In water, no. In organic solvents (e.g., alcohols), yes
53
What is the most common type of oil that makes up fats and oils
Triglyceride
54
What is the structure of a triglyceride
3 fatty acid chains each bonded by an ester bond to a molecule of glycerol through condensation reactions
55
What are the functions of triglycerides
Comprise cell membranes, insulation, energy source, waterproofing and protection
56
What are the isomers of fatty acids that are found in triglycerides
Unsaturated (no carbon-carbon double bonds), Monounsaturated (1 carbon-carbon double bond), Polyunsaturated (more than 1 carbon-carbon double bond)
57
How do double bonds affect the displayed structure of a fatty acid chain
Cause a kink
58
Where are unsaturated fatty acid triglycerides mainly found
Fish, vegetable oils, nuts
59
Where are saturated fatty acid triglycerides mainly found
Animal fats
60
What is the name of the process where a triglyceride is formed
Esterification
61
How many molecules of water are lost during one esterification reacted
3
62
How is the structure of a triglyceride adapted to its function
- Energy source - high ratio of C-H bonds
- Low mass to energy ratio good for storage as lots of energy stored in a small
volume
- Large and non-polar - Insoluble so does not affect osmosis or water potential of cells
- High ratio of H to O atoms - source of water as release water when oxidised
(important if living in dry conditions)
62
How is a phospholipid's structure different to a triglyceride's structure
2 fatty acid chains and a phosphate group bonded on the opposing side of the glycerol, each bonded by an ester bond to a molecule of glycerol through condensation reactions
63
What are the functions of a phospholipid
Form a bilayer cell membrane
64
How is the structure of a phospholipid adapted to its function
- Polar molecules - form a bilayer in a aqueous environment
- Hydrophilic heads - allow the bilayer to form and hold it in position
- Phospholipid heads - allows formation of glycolipids
65
Which section of a phospholipid is polar and why
The heads, the phosphate group is negatively charged
66
Which section of a phospholipid is non - polar and why
The tails, no charged ions
67
Which section of a phospholipid is hydrophilic and why
The head, it is polar so can therefore hydrogen bond with the water
68
Which section of a phospholipid is hydrophobic and why
The tails, they are non-polar so can't hydrogen bond with the water
69
What is the general formula of an amino acid
N(H2)C(HR)C(OOH)
70
How many different amino acids are there
20
71
What is a polypeptide
A long chain of amino acid monomers bonded together through peptide bonds formed through condensation reactions
72
Where does a peptide bond form in a di/polypeptide
Between the amine group (loses 1 H) and the carboxyl group (loses 1 OH), bond runs from N to C
73
What are the 4 different level of protein structure
Primary, secondary, tertiary, quaternary
74
What is the primary structure of a protein
The order of amino acids in the polypeptide chains.
75
What determines the order of amino acids in the tertiary structure
The sequence of the nucleotidesin DNA
76
What is the secondary protein structure
The way the primary protein structure is folded
77
What determines the shape in the secondary protein structure
The location of hydrogen bonds between the amine groups and carboxyl group
78
What is the main form of the secondary protein structure
Alpha helix
79
What is the secondary form of the secondary protein structure
Beta pleated sheet
80
How do the bonds in the secondary protein structure aid its function
The high abundance of hydrogen bonds keeps the alpha helix stable and reduces the risk of external mutationary effects
81
What is the tertiary protein structure
The unique, complex, compact, 3D globular structure formed by the folding of the secondary protein structure
82
Why are tertiary proteins unique
So they are the sole type of protein that can perform its specific function (most are enzymes)
83
What are the different kinds of bonds in the tertiary protein structure
Disulphide (between amino acids that contain sulphur - covalent and strong), Ionic (between R-groups with positive or negative
charges - weaker than disulphide and easily broken by changes in pH),
Hydrogen (between the ‘R’ groups, are weak individually but highly abundant)
84
What is the quaternary protein structure
How the different polypeptide chains (tertiary structures) are arranged together
85
What does the tertiary structure of a fibrous protein look like
Long
86
What are fibrous proteins use for and why
Structural measures, insoluble and strong
87
What are globular proteins used for and why
Involved in cellular metabolism (e.g. enzymes; receptor proteins, protein hormones and antibodies), specific and unique tertiary structure hydrophilic / soluble
88
What is the test for reducing sugars
Benedict's test
89
What is the test for non-reducing sugars
Modified benedict's test
90
What is the test for starch
Iodine test
91
What is the test for lipids
Emulsion test
92
What is the test for proteins
Biuret's test
93
How is the benedict's test carried out
- Food sample dissolved in water is mixed with
an equal volume of Benedict's reagent
- Mix and heat in a water bath at 80-90◦C
- If the solution turns orange, a reducing sugar
is present
94
How is a modified benedict's test carried out
- The sample or solution under consideration is boiled for at least fifteen minutes in hydrochloric acid (Boiling in acid breaks glycosidic bonds – the glycosidic bond is hydrolysed – This is called ACID HYDROLYSIS)
- The solution is then neutralised by adding drops of alkali such as sodium hydrogen carbonate
- Benedict’s test is now performed on the resulting
solution
- If a brick-red precipitate forms then sucrose was
present in the original solution
95
Why may a disaccharide be non-reducing
It can't reduce copper (ii) ions
96
How is an iodine test carried out
- The sample should have iodine dropped on it, taking care not to oversaturate it
- If the sample turns blue/black, starch is present
97
How is an emulsion test carried out
- Add an equal or lesser amount of alcohol to the solution
- Shake
- Add an equal volume of distilled water
- If a lipid is present a cloudy white emulsion will form
98
How is a biuret's test carried out
- Add equal volumes of copper sulphate and sodium hydroxide to
the solution
- If a protein is present, it will turn violet.
99
What is an enzyme
A globular protein that acts as a biological catalyst with a unique and specific tertiary structure and active site that bonds with a specific substrate to form an enzyme substrate complex, which lowers the activation energy needed for a chemical reaction
100
How is the shape of an enzyme adapted to its function
- Specific 3D tertiary structure
- Substrate complementary shape to active site
- Substrate can bind to active site
101
What are the two models of how an enzyme works
Lock and key, induced fit
102
What is the lock and key theory
- The enzymes’ active site is a specific shape due to its tertiary structure.
- The substrate has a complementary shape to the active site, and it fits in like a key fitting into a lock
- Temporary structure called the enzyme-substrate complex formed
- Products have a different shape from the substrate
103
What is the induced fit model
- The enzyme’s active site is not exactly the same shape as the substrate
- Active site moulds itself around the substrate as the enzyme substrate complex is formed
- This explains why enzymes that can react with a range of substrates of similar types
104
How is gradient calculated on a rate of reaction graph
rise / run
105
What factors can affect the rate of enzyme catalysed reactions
Temperature, pH, Enzyme concentration, Substrate concentration, Inhibitors
106
How does temperature affect the rate of enzyme catalysed reactions
- As the temperature increases the Kinetic Energy of the molecules increases.
- They move about more quickly and collide more so frequency of successful
collisions increases.
- The reaction goes faster until the optimum temperature
- Above the optimum temperature hydrogen bonds holding the enzyme’s tertiary structure in place start to break.
- The active site shape changes shape and can’t bind the substrate so less enzyme substrate complexes
- The enzyme is denatured & the reaction slows
107
How does pH affect the rate of enzyme catalysed reactions
- The change in H+ affects the charge on the amino acid
- This causes (ionic) bonds in the tertiary structure to break
- This alters the tertiary structure distorting the active site shape
- Substrate can no longer bind so no enzyme substrate complexes are
formed
108
What is pH
The measure of the concentration of hydrogen ions in a solution
109
How can a small change in pH affect an enzyme catalysed reaction
A small change in pH can affect the charge on the amino acids that make up the active site thereby changing the shape of the active site so the substrate can no longer fit into to bind to it
110
How can a large change in pH affect an enzyme catalysed reaction
A large change in pH breaks ionic bonds in the enzyme structure. The tertiary structure breaks, changing the enzyme’s shape. The active site changes shape and the substrate can no longer fit into to bind to it
111
How can substrate concentration affect an enzyme catalysed reaction
The increasing amount of substrate can bind to
active sites on the enzymes as more successful
collisions occur. At this point, the amount of substrate is limiting because as the rate is increasing as the
concentration of substrate also increases. Once every enzyme active site is occupied, adding more substrate makes no difference. At this point, the concentration of substrate is no longer limiting, something else is
112
What are enzyme inhibitors
Substances that directly or
indirectly interfere with the functioning of the active
site of an enzyme
113
What are the two types of enzyme inhibitors
Competitive and non-competitive
114
How does competitive inhibition work
A competitive inhibitor molecule has a similar
structure to the normal substrate molecule, and it
can fit into the active site of the enzyme. The inhibitor is not permanently bound to the active site. When it leaves another molecule takes its place
115
In what situation does the competitive inhibitor successfully compete for the active sites
When substrate concentration is low
116
Can competitive inhibition be overcome
- Yes, the effect of the competitive inhibitor is overcome when the high concentration of substrate molecules competes
successfully for the active sites of the enzymes
- At high substrate concentration, maximum reaction rate is achieved
117
How do non-competitive inhibitors work
- A non-competitive inhibitor molecule has a different
structure from the substrate molecule
- It binds to another part of the enzyme molecule causing the shape of the whole enzyme to change, so the active site changes and it can no longer bind substrate molecules.
118
Can non-competitive inhibition be overcome
- No, high substrate concentration has no effect because the molecules are
not competing for the same binding site
- Maximum rate of reaction not
reached
119
How does potassium cyanide act as an inhibitor poison
- Inhibits a vital respiratory enzyme called cytochrome oxidase (found inside
mitochondria)
- Cytochrome oxidase normally combines oxygen and hydrogen together to form water and allows ATP creation.
- Cyanide non-competitively inhibits chytochrome
oxidase changing the shape of its active site meaning no ATP creation.
- Any reactions requiring ATP are no longer supplied. The body eventually has no energy supply causing total cell failure
-
120
How does the fasciculation protein in snake venom act as an inhibitor poison
- Inhibits Acetylcholinesterase which is an enzyme used to degrade a neurotransmitter called Acetylcholine
- Fasciculation acts as a competitive inhibitor preventing the acetylcholine from being broken down by
Acetylcholinesterase after an impulse transmission.
- In skeletal muscle fasciculations stop nerve impulses from being transmitted and hence stop muscle contraction.
- Eventually this will lead to flaccid paralysis.
121
How do HIV Protease inhibitors act as medical inhibitors
- Competitively inhibits HIV virus protease enzymes.
Normally the virus uses this to cut viral RNA into smaller pieces so as into implant genes into the host cells DNA and hence replicate
- The inhibitor binds specifically with the HIV protease enzymes active site preventing longer viral RNA pieces from bindings, as a result the RNA is not cut into smaller pieces so it cannot be implanted into the host cells DNA = no replication
- A host cell can be infected by HIV but it cannot be ‘hijacked’ into making more HIV copies as a result of DNA implantation by the
virus
